This invention relates to an image forming apparatus, such as a printer, and a method of saving consumption of toner, particularly to the image forming apparatus and the method of saving consumption of toner without deterioration of printing quality.
Conventionally, in order to save a consumption of toner, a toner density adjusting volume is provided in an image forming apparatus, such as a printer. When printing must be done with the toner being saved, the printing is done with lower density of toner by adjusting the toner density adjusting volume. However, in such a method, it is required to readjust the toner density adjusting volume when a normal printing is desired.
Under the circumstances, some proposals are made to save the consumption of toner without adjusting such a volume.
A proposal is exemplified, as a first prior art, in unexamined Japanese Patent Publication No.Hei 6-24043, namely, 24043/1994. The first prior art has a data transmission portion for transmitting dot image data to a print head as a video signal, and a thinning portion positioned between the data transmission portion and the print head. The thinning portion detects a specific dot pattern which consists of a plurality of same dot patterns sequentially located. Then, the thinning portion converts each black dot positioned in both ends of a sequence of black dots into each white dot in the specific dot pattern data.
On the other hand, an another proposal is exemplified, as a second prior art, in unexamined Japanese Patent Publications No.Hei 2-144574, namely, 144574/1990. In the second prior art, a consumption of toner can be saved responsive to numbers of skipped dots, by skipping numbers of dots consisting of a character and carrying out printing lo based on dot data thus skipped.
Further, a still another proposal is exemplified, as a third prior art, in unexamined Japanese Patent Publications No.Hei 7-107280, namely, 107280/1995. The third prior art has a distinguishing portion for distinguishing a contour of image data from an inner portion thereof. A toner saving mode is applied to the inner portion with each one pixel constituting the contour of the image data being remained. Accordingly, deterioration of quality of image is prevented.
By the use of methods of saving a consumption of toner thus mentioned as the first, the second, and the third prior arts, it becomes possible to save the consumption of toner in spite of the printing with lower density of toner after adjusting the toner density adjusting volume.
However, in these prior arts, saving of toner is achieved by reducing black dot data. As a result, smoothness of a character, a circle, and a line is deteriorated. For example, a fine character is thereby deformed in a printed manner. It is Inevitably caused to occur that the deformed fine character cannot be read with ease.
It is a recent trend that an image forming apparatus, such as a printer, has a higher resolution and that various fonts are used in the image forming apparatus. Under the trend, if Roman-type characters in which a weight of a character varies are subjected to the thinning operation, for example, of the first prior art, the Roman-type characters becomes more blurred. In the third prior art, a toner saving is sometimes applied with each one pixel constituting the contour of the image data being remained. A width of one dot line becomes not more than 0.021 mm (0.042 mm in a case of 600 dpi) to produce an extremely fine line. By these characteristics, toner is not attached to the contour portion, so that the contour is disappeared. Consequently, deterioration of quality of image becomes inevitable.
It is therefore an object of the present invention to provide an image forming apparatus which is capable of saving consumption of toner without deterioration of printing quality and a method thereof.
Other objects of this invention will become clear as the description proceeds.
According to an aspect of this invention, there is provided an image forming apparatus which is for use in printing data sent from an upper apparatus, said image forming apparatus comprising: spreading means for spreading said data sent from said upper apparatus into bit map data consisting of dot data; storing means for storing said bit map data spread by said spreading means; extracting means for extracting contour-protecting shaped matrix data having a contour-protecting shape which prevents a contour of image from being disappeared; and printing means for printing said dot data based on said contour-protecting shape.
The image forming apparatus may be a printer.
The contour-protecting shaped matrix data may comprise 3xc3x973 pixels, two pixels added in upper and lower sides, respectively, and further two pixels added in left hand and right hand sides, respectively.
The template data may be composed of all black dots in the same shape as that of said contour-protecting shaped matrix data.
The image forming apparatus may further comprise template data memorizing means for memorizing template data which previously define a standard shape of a character and a symbol.
The image forming apparatus may further comprise toner consumption saving pattern memorizing means for memorizing toner consumption saving pattern data which corresponds said standard shape of said character and said symbol.
The image forming apparatus may further comprise toner consumption control means for forming a final shape which is printed finally based on each of said contour-protecting shaped matrix data, said template data, and said toner consumption saving pattern data.
According to another aspect of this invention, there is provided a method of saving consumption of toner of an image forming apparatus for use in printing data sent from an upper apparatus, said method comprising the steps of: spreading said data sent from said upper apparatus into bit map data consisting of dot data; storing said bit map data spread in said spreading step; extracting contour-protecting shaped matrix data having a contour-protecting shape which prevents a contour of image from being disappeared; and printing said dot data based on said contour-protecting shape.
The method may further comprise the step of memorizing template data which previously define a standard shape of a character and a symbol.
The method may further comprise the step of memorizing toner consumption saving pattern data which corresponds said standard shape of said character and said symbol.
The method may further comprise the step of controlling toner consumption to form a final shape which is printed finally based on each of said contour-protecting shaped matrix data, said template data, and said toner consumption saving pattern data.